Study of overall and local electrochemical responses of oxide films grown on CoCr alloy under biological environments

The interaction of the physiological medium and living tissues with the implant surfaces in biological environments is regulated by biopotentials that induce changes in the chemical composition, structure and thickness of the oxide film. In this work, oxide films grown on CoCr alloys at 0.5 V vs Ag/AgCl and 0.7 V vs Ag/AgCl have been characterized through overall and localized electrochemical techniques in a phosphate buffer solution and 0.3% hyaluronic acid. Nanopores of 10–50 nm diameter are homogeneously distributed along the surface in the oxide film formed at 0.7 V vs Ag/AgCl. The distribution of the Constant Phase Element studied by local electrochemical impedance spectroscopy showed a three-dimensional (3D) model on the oxide films grown at 0.5 V vs Ag/AgCl and 0.7 V vs Ag/AgCl. This behaviour is especially noticeable in oxide films grown at 0.7 V vs Ag/AgCl, probably due to surface inhomogeneities, and resistive properties generated by the potentiostatic growth of the oxide film.This work was supported by the Spanish National government [MINECO-MAT2011-29152-C02-01].Peer reviewe

Chemical conversion treatments to protect biodegradable magnesium in applications as temporary implants for bone repair

7 páginas, 7 figuras, 1 tabla.[ES] El presente estudio se desarrolló para mejorar la resistencia a la corrosión del magnesio puro, modificando su superficie mediante recubrimientos de conversión química. Se generaron capas de carbonato y fluoruro por inmersión en soluciones de NaHCO3 al 9 % y de HF al 48 %, respectivamente. La resistencia a la corrosión de las muestras con recubrimiento se evaluó en comparación con la del sustrato desnudo mediante técnicas electroquímicas en una solución fisiológica (PBS). Los resultados obtenidos han mostrado que el recubrimiento de carbonato no es capaz de proteger de la degradación al sustrato de magnesio. Por el contrario, el recubrimiento de fluoruro ha demostrado aumentar, significativamente, la resistencia a la corrosión del magnesio en medio fisiológico. La alta compacidad y adherencia al sustrato metálico de la capa de MgF2 generada mediante este sencillo tratamiento de conversión química confieren al recubrimiento buenas propiedades protectoras.[EN] The present study was developed to improve the corrosion resistance of pure magnesium by applying chemical conversion coatings. Carbonate and fluoride layers were generated by immersion in solutions of NaHCO3 of concentration 9 wt.%and HF of concentration 48 wt.%, respectively. Corrosion resistance of the coated samples was evaluated in comparison with that of the uncoated substrate by electrochemical techniques in a physiological solution (PBS). Results have shown that the carbonate coating is not viable to be used for protecting magnesium against corrosion.On the contrary, the fluoridemagnesiumcoating significantly increases the corrosion resistance ofmagnesium in physiological medium. The high compactness and adherence to the base metal of theMgF2 layer produced by this simple chemical conversion treatment confer the protective properties to the coating.Los autores agradecen al MEC la financiación del proyecto con referencia MAT 2008-06719-C03-01. M. Carboneras agradece al CSIC la concesión de un contrato JAE-Doc.Peer reviewe

Preparación de recubrimientos de hidroxiapatita a partir de precursores de tipo sol-gel

Desde los años 90, se realizan innumerables investigaciones para obtener un sistema que combine las ventajas mecánicas de los metales y la afinidad biológica de las cerámicas de hidroxiapatita. Recubrimientos de hidroxiapatita obtenidos vía sol-gel se han utilizado con estos propósitos. Se presentan los resultados preliminares de un estudio integrado en el que se contemplan aspectos tan diversos como son el diseño, preparación, caracterización y evaluación del comportamiento frente a la corrosión de nuevos recubrimientos de hidroxiapatita para aplicaciones biomédicas; sobre la superaleación de titanio del tipo MA956 de composición nominal Fe-20 Cr-5 Al-0,5 Ti-0,5 Y2O3. Sobre dicha superaleación se aplicó previamente un tratamiento térmico para producir una película homogénea y compacta de a-alumina, que actúa como barrera frente a la corrosión del sustrato metálico que posteriormente fue tratada adecuadamente antes de realizar el recubrimiento de hidroxiapatita. La capa de hidroxiapatita depositada sobre el sustrato metálico, fue preparada usando una variante del proceso sol-gel utilizado por D. M. Liu en medio alcohólico y posteriormente cristalizada por la novedosa técnica de tratamiento térmico a velocidad controlada. El recubrimiento resultante de hidroxiapatita fue caracterizado mediante el modo de reflexión de espectroscopia infrarroja de transformada de Fourier (FTIR), difracción de rayos-x de ángulo rasante (DRX), microscopia electrónica de barrido con análisis por microsonda (MEB/EDX) y espectroscopia fotoelectrónica de rayos-x (XPS). Los análisis de FTIR y DRX revelaron la cristalinidad de la fase y la homogeneidad en la composición química de la hidroxiapatita formada, corroborados por los resultados obtenidos por XPS

Preparación de recubrimientos de hidroxiapatita a partir de precursores de tipo sol-gel

Desde los años 90, se realizan innumerables investigaciones para obtener un sistema que combine las ventajas mecánicas de los metales y la afinidad biológica de las cerámicas de hidroxiapatita. Recubrimientos de hidroxiapatita obtenidos vía sol-gel se han utilizado con estos propósitos. Se presentan los resultados preliminares de un estudio integrado en el que se contemplan aspectos tan diversos como son el diseño, preparación, caracterización y evaluación del comportamiento frente a la corrosión de nuevos recubrimientos de hidroxiapatita para aplicaciones biomédicas; sobre la superaleación de titanio del tipo MA956 de composición nominal Fe-20 Cr-5 Al-0,5 Ti-0,5 Y2O3. Sobre dicha superaleación se aplicó previamente un tratamiento térmico para producir una película homogénea y compacta de a-alumina, que actúa como barrera frente a la corrosión del sustrato metálico que posteriormente fue tratada adecuadamente antes de realizar el recubrimiento de hidroxiapatita. La capa de hidroxiapatita depositada sobre el sustrato metálico, fue preparada usando una variante del proceso sol-gel utilizado por D. M. Liu en medio alcohólico y posteriormente cristalizada por la novedosa técnica de tratamiento térmico a velocidad controlada. El recubrimiento resultante de hidroxiapatita fue caracterizado mediante el modo de reflexión de espectroscopia infrarroja de transformada de Fourier (FTIR), difracción de rayos-x de ángulo rasante (DRX), microscopia electrónica de barrido con análisis por microsonda (MEB/EDX) y espectroscopia fotoelectrónica de rayos-x (XPS). Los análisis de FTIR y DRX revelaron la cristalinidad de la fase y la homogeneidad en la composición química de la hidroxiapatita formada, corroborados por los resultados obtenidos por XPS

Effect of wear-corrosion of reduced graphene oxide functionalized with hyaluronic acid on inflammatory and proteomic response of J774A.1 macrophages

The presence of a worn surface in the implanted material, as in the case of a replacement of a damaged osteoarticular joint, is the normal condition after implantation. This manuscript focuses precisely on the comparative study of the cellular behavior on worn CoCr surfaces, analyzing the effect of different surface modifications on macrophages’ responses. CoCr surfaces were modified by the deposition of electrochemically reduced graphene oxide (CoCrErGO), followed by additional surface functionalization with hyaluronic acid (CoCrErGOHA). After the wear corrosion processes, the macrophage response was studied. In addition, macrophage supernatants exposed to the surfaces, before and after wear, were also evaluated for osteoblast response through the analysis of the metabolic activity, plasma membrane damage, and phosphatase alkaline activity (ALP). The proteomic analysis and the quantitative TNF-α/IL-10 ratios of the J774A.1 macrophages exposed to the surfaces under study showed a polarization shift from M0 (basal state) to M1, associated with the pro-inflammatory response of all surfaces. A lower M1 polarization was observed upon exposure to the surface modification with ErGO, whereas posterior HA functionalization attenuated, even more, the M1 polarization. The wear corrosion process contributed to inflammation and exacerbated the M1 polarization response on macrophages to CoCr, which was diminished for the ErGO and attenuated the most for the ErGOHA surfaces. Comparative proteomics showed that the pathways related to M1 polarization were downregulated on the surfaces of CoCrErGOHA, which suggests mechanisms for the observed attenuation of M1 polarization. The suitable immuno-modulatory potential induced by the ErGOHA surface, with and without wear, together with the stimulation of ALP activity in osteoblasts induced by macrophage supernatants, promotes the mineralization processes necessary for bone repair. This makes it feasible to consider the adsorption of ErGOHA on CoCr as a recommended surface treatment for the use of biomaterials in osseous joint applications.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Corrosión in vitro e in vivo de las prótesis mixtas acero inoxidable-cerámica

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Sección de Químicas. Fecha de lectura: 1-05-198

Synthesis and Electrochemical Characterisation of Magnetite Coatings on Ti6Al4V-ELI

© 2020 by the authors.Titanium alloys have been widely employed in implant materials owing to their biocompatibility. The primary limitation of these materials is their poor performance in applications involving surfaces in mutual contact and under load or relative motion because of their low wear resistance. The aim of this work is to synthesis magnetite coatings on the Ti6Al4V-ELI alloy surface to increase corrosion resistance and to evaluate its electrochemical behaviour. The coatings were obtained using potentiostatic pulse-assisted coprecipitation (PP-CP) on a Ti6Al4V-ELI substrate. The preliminary X-Ray Diffraction (XRD) results indicate the presence of the magnetite coating with 8–10 nm crystal sizes, determined for the (311) plane. Using X-ray photoelectron spectroscopy (XPS), the presence of the magnetite phase on the titanium alloy was observed. Magnetite coating was homogeneous over the full surface and increased the roughness with respect to the substrate. For the corrosion potential behaviour, the Ti6Al4V-ELI showed a modified Ecorr that was less active from the presence of the magnetite coating, and the impedance values were higher than the reference samples without coating. From the polarization curves, the current density of the sample with magnetite was smaller than of bare titanium.This research was funded by Instituto Politécnico Nacional, Consejo Nacional de Ciencia y Tecnología (CONACyT), Proyecto SIP 20195816, and Centro Nacional de Investigaciones Metalúrgicas (CENIM-CSIC) Madrid, España supported this project.Peer reviewe

Corrosion behaviour of FeAl-type intermetallic compounds

In this study, the corrosion behaviour of two different iron aluminides based on FeAl, with two different microstructures, in a chloride-containing solution (pH = 7.4), has been investigated using electrochemical techniques. Both materials were studied in as-received condition and also after heat-treatment at 1100°C for two hours. This thermal process was performed to generate an alumina layer on the intermetallic surface with the purpose of improving its corrosion resistance. The polarization resistance method and the electrochemical impedance spectroscopy reveal similar corrosion resistance values for all samples although the corrosion attack produced is different. This result indicates that for these intermetallic alloys the alumina layer generated after two hours heat treatment is a low protecting layer due to the presence of additional oxides. Visual and optical microscopic observation of the sample surfaces reveal the formation of surface corrosion attack after the fourth day of immersion in the electrolyte for almost all samples. For samples without initial pits the anodic polarization curves showed a low pitting corrosion resistance. © 1997 Elsevier Science Ltd.This work has been supported by the project MAT95-0249-C03-01 of the Spanish Comisión Interministerial de Ciencia y Technologı́a (CICYT) and the CEASI programme on Fe aluminides.Peer Reviewe

3D, chemical and electrochemical characterization of blasted TI6Al4V surfaces: Its influence on the corrosion behaviour

The blasting process to increase the roughness of the surface of metallic biomaterials is widely used. As a consequence, one can produce a renewed surface with different topography and chemical composition compared to the original one, which can alter the general corrosion behaviour of the samples. With this idea, the aim of this work is not only the topographical and compositional characterization of blasted surfaces of Ti6Al4V alloy but mainly its influence on the corrosion behaviour of these modified surfaces. The surfaces of Ti6Al4V alloys were blasted with SiO2/ZrO2 and Al2O3 particles of different size in order to obtain different roughnesses. To carry out the microstructural and topographical characterization of the blasted surfaces, the scanning electron microscopy (SEM) coupled with an energy dispersive X-ray (EDX), the contact profilometry method and the 3D characterization by means of stereo-Fe-SEM have been used. By means of stereo-Fe-SEM, the roughness and the real surface area of the rough surfaces have been calculated. The microstructural, topographical and compositional results have been correlated with the corrosion behaviour of the samples immersed in Hank's solution and studied by means of electrochemical impedance spectroscopy (EIS). The blasting process alters topographical and chemically the surface of the samples. These modifications induce to an increase in the capacitance values of the roughened samples due to the prevalence of the effect of electrochemically active areas of Ti6Al4V surface over the effect of the presence of Al2O3 and ZrO2 particles on the blasted surfaces. However, the general corrosion behaviour of the samples is not drastically changed. © 2007 Elsevier Ltd. All rights reserved.Peer Reviewe

Corrosion of reinforcing steel in mortar of cement with CaF2 as a minor component

This paper reports on the corrosion behaviour of steel embedded in mortar of cement manufactured using CaF2 as a mineraliser and flux agent. Corrosion rates of steel in this new cement measured with electrochemical techniques are compared with the corrosion rates of steel in contact with a traditional cement of similar characteristics in the same conditions. It was confirmed that the new cement does not lead to pitting corrosion and corrosion rates of steel are similar to traditional cement even in presence of corrosive agents such as chlorides or carbonation of cement. © 1995 Elsevier Science Ltd All rights reserved.Peer Reviewe